1. Field of the Invention
This invention relates to improvements in integrated circuits and integrated circuit techniques, and more particularly to improvements in ground bounce compensation circuits for use in integrated circuits and methods for constructing and using same.
2. Relevant Background
Numerous circuits are used in digital bipolar devices which address the problem of ground falling below zero volts as transistors are switched on and off. This phenomenon is referred to as "negative ground bounce," or "NGB." However, also of concern are instances in the operation of integrated circuits in which the ground potential increases to undesirably high positive levels. This may result in propagation of erroneous data, in some cases, and may result in the damage or destruction of sensitive integrated circuit components, as well. Nevertheless, providing a circuit that alleviates the problem of the ground potential increasing positively ("positive ground bounce", or "PGB") to undesirable high positive voltage levels has not been sufficiently addressed.
Although this problem exists in many integrated circuit configurations, it is especially pronounced in integrated circuit that are used to switch more than one output. In such embodiments, the ground potential tends to become unstable as current is driven into it simultaneously from mere than one output.
In some configurations, this problem has been addressed by the circuit designer taking measures to reduce the upward ground bounce. Examples of this approach can be seen in many bipolar digital octal devices, which include means for reducing the amount of voltage ground movement. Techniques such as reducing the amount of base drive to output NPN transistors and decreasing the output drive capability of these devices were commonly used. These approaches, however, usually sacrificed the AC speed performance of the circuit.
What is needed, therefore is a circuit that compensates for positive ground bounce or movement, which can be used in integrated circuits, in general, and in integrated circuits of the type that have more than one output, in particular.